This is one of the largest fears that I have living on the River Road. There is a lot of industry upriver from me and there were two leaks in two days last week.
1*Cytec is about 2 miles from me and they had a large ammonia leak that you instantly noticed the second you stepped outdoors. Luckily it dissapated in a few hours.
2*The next day Dow (Union Carbide) which is about 15 or 20 miles upriver had a leak that stunk like he77 and they refused to identify it for hours. I guess they had to consult with their legal department first to find out what to say. Then they said it was such a minor leak that it posed no hazard. Of course, the police that had the road blocked off around the area were all wearing gas masks. They could smell this "minor" leak 30 miles away.
Visions of Bhopal India were floating through our minds as we recalled that dreadful day 25 years ago that Union Carbide had a leak of "unidentified" gas there that instantly killed 10,000 people and injured 500,000 more.
Later that day they identified this gas as Ethyl Acrylate, naturally claiming that it was too low of a concentration to cause harm even though it is a suspected carcinogen.
The nuclear plant about 30 miles away has sirens all around to notify people of an emergency but the chemical plants do their best to keep it a secret if they have a spill and only tell what they are forced to reveal.